Davison–Meinhardt [1]} proved a
Poincaré-Birkhoff-Witt (PBW) theorem beyond the case of \(\left(\widetilde{Q}, \widetilde{W}\right)\) , namely for all pairs \((Q,W)\)  where \(Q\)  is symmetric.
Let \(X(d)\)  be the coarse space of \(\mathcal {X}(d)\) . The coarse space map
\(\pi : \mathcal {X}(d)\rightarrow X(d)\) 
